1. Field of the Invention
This invention relates to a method for improving color removal activity of aged hydrofinishing catalyst exhibiting reduced color removal activity. In particular, it relates to contacting such an aged catalyst with a small amount of added elemental sulfur dissolved in hydrocarbon oil, such as the feed oil to the hydrofinishing process utilizing said aged catalyst, at mild contact conditions.
2. Description of the Prior Art
In hydrofinishing a lubricating oil for upgrading color thereof a continuous increase in processing temperature is necessary for maintaining color activity of the hydrofinishing catalyst utilized in the process at an acceptable level. Since high hydrofinishing temperatures are detrimental to oxidation stability of a finished oil, a hydrofinishing process wherein steadily increasing temperature are required to maintain color activity of the catalyst fast approaches non-utility. The present method allows continuing use of lower hydrofinishing temperatures and, in fact, quite mild hydrofinishing process conditions throughout a hydrofinishing process by improving or maintaining catalyst color activity at those mild conditions. The present method eliminates the need for process shutdown for the purpose of regenerating the hydrofinishing catalyst relative to color removal activity. No method is known at present which so effectively and easily alleviates the above processing problems as the present invention.